Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/18/23

National Weather Service Bismarck ND
857 PM CDT Mon Apr 17 2023 .UPDATE... Issued at 854 PM CDT Mon Apr 17 2023 Nothing to update at this time of the night. UPDATE Issued at 624 PM CDT Mon Apr 17 2023 Only adjusted the timing of the patchy fog in the James River Valley as the RAP has some fog between 9-11z. Confidence is low in the fog however. && .SHORT TERM...(This Evening through Tuesday) Issued at 247 PM CDT Mon Apr 17 2023 Current surface analysis places low over the Great Lakes into eastern Ontario, with ridge stretching through the eastern plains. Upper level analysis places low off the northwest Pacific coast, with ridge over the northern plains. Over our area, rather quiet weather remains, with a southeasterly breeze to the east of the surface ridge over western parts of our area. For tonight, a weak initial short wave slides mainly over western portions of the area as upper ridge does a gradual progression east. This may bring a little light rain over western areas. On Tuesday, upper ridge continues to scoot over to the east as a stout short wave swinging around the base of the Pacific ridge works its way towards the Rockies. Elongated surface lee trough deepens, resulting in breezy southeasterly winds over the area. Precipitation chances from earlier mentioned initial wave lift north, but chances with the second more stout wave will be increasing in the afternoon. .LONG TERM...(Tuesday Night through Monday) Issued at 247 PM CDT Mon Apr 17 2023 As we go through Tuesday night, short wave starts to close off over eastern Montana, while surface low lifts and deepens along the Montana/North Dakota border. Precipitation spreads over the area, with snow developing over the far north, mainly rain elsewhere. Over southern locations, some instability is noted which may lead to a few claps of thunder. As we go through Wednesday, surface low lifts north/northeast with the system, then stack up and lingers over north central North Dakota. This will lead to winds becoming westerly over the southwest, becoming quite gusty. Precipitation starts to wane over the south with the lifting system, but continues over the north. Where this becomes a bit concerning is primarily over the far northwest where cold air gets wrapped into the system, and snow continues, while further east/south more of a mix is expected through the day before transitioning overnight while chances stat to wane. NBM probabilities have increased a fair amount for the possibility of over 6 inches along and north of Highway 2 (~50-75%), though this includes going into Thursday. There are some concerns on the potential impact with this as we are in the time of year where insolation is similar to that of later August, so when snow rates are lower, expect melting on roadways. Either way, roads may be quite crummy overnight given freezing temperatures. On Thursday, greatest chances spread again through the north while upper low starts to drop east-southeast, then eventually makes its exit though chances do linger through Friday. Drier conditions expected for the weekend, though temperatures will be cooler. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening) Issued at 624 PM CDT Mon Apr 17 2023 VFR through the period with chances of rain across the north starting overnight and breezy southeast winds at 30 knots through Tuesday. Low confidence in fog at KJMS so left it out for now. Clouds will move in overnight. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Smith SHORT TERM...JJS LONG TERM...JJS AVIATION...Smith
Area Forecast Discussion
National Weather Service Pendleton OR
834 PM PDT Mon Apr 17 2023 .UPDATE...Current radar and infrared satellite imagery showing light to moderate returns along the Blue Mountain Foothills and extending east into the Lower Columbia Basin under mostly cloudy skies. These returns are associated with isolated storm cells that have been developing through this afternoon and are continuing into the evening hours. Spotter reports and observations have indicated that pea size hail and wind gusts of up to 40 mph have occurred within this afternoon`s storm cells. However, storm intensity will be waning through the remainder of the evening with the lack of daytime heating. Showers are still expected along the Blue Mountains/foothills and east overnight before lingering over higher elevations of the Cascades, Blue, and Eastern Mountains into Tuesday morning. Increased PoPs and QPF over areas of the Lower Columbia Basin and Blue Mountain Foothills to better account for developing showers and isolated storms with this evening`s forecast update, along with minor edits to sky cover, temperatures, and winds to better align with current observations and recent guidance. Current highlights do look to verify as over 5 inches is expected along the east slopes of the Oregon Cascades above 4500 feet, and overnight low temperatures are likely to reach near 27 degrees in the Yakima and Kittitas Valleys. 75 && .PREV DISCUSSION... /issued 448 PM PDT Mon Apr 17 2023/ ..Updated Aviation Discussion... SHORT TERM...Today through Wednesday...An offshore low centered off the BC coast will circulate rounds of precip into the forecast area over the next several days, as well as drive unseasonably cool temperatures through much of the work week. For today, a frontal boundary associated with this low is beginning to push through the Cascades, with a combination of SW flow aloft and upslope flow beginning to spawn scattered showers ahead of the front. While instability will be limited due to the cooler-than-average conditions we`ve experienced since yesterday, both the synoptic setup and convective parameters support a few isolated thunderstorms, primarily across the mountains of central OR into the eastern mountains. Most recent CAMs have backed off a tad on depicting more organized convective cells across the eastern half of the CWA, with the offshore low beginning to develop enough of a negative tilt to push the main front more north and east of us, but could still see convection and a few rumbles a thunder across the foothills of the Blues into the mountains themselves, even where snow levels are low enough to support snow. Orographic lift, combined with a well-saturated environment and strong lapse rates, should be enough to overcome these relatively cool temperatures for thunderstorms. As far as mountain snow is concerned, the threat will be primarily limited to the OR Cascades, where snow levels are low enough to support accumulating snow at the pass level. A Winter Weather Advisory is in effect for this area through Tuesday morning, highlighting primarily the Santiam Pass area for any evening and early morning commuters. A few inches of snow may also occur in the Blues above 4000 ft. Precip threat largely diminishes by daybreak Tuesday, as the upper- level flow pattern becomes more zonal, allowing drier conditions to prevail. Such a pattern would support only some light isolated shower activity across our high mountains. Precip threat re-emerges on Wednesday as the aforementioned low circulates another wave through the interior Northwest. This weaker system will lead to a more diminished threat across our lower elevations, with models pinpointing primarily our mountain zones once again for precip Wednesday. Snow levels look to be around 2000-3000 ft. Instability doesn`t look to be as strong as Monday`s setup, but NAM and RAP do key in on some low MUCAPE over the eastern mountains. As of now, any activity looks again to be isolated in nature. Freeze warnings continue for the Yakima and Kittitas Valleys due to this offshore low allowing colder, northerly air to filter in. Expect lows to dip into the upper 20s both Tuesday and Wednesday morning for these areas, especially as the bulk of moisture transport from this system falls to the areas` south and east. Highs will remain primarily in the upper 40s into 50s across our population centers through the short term period. Evans/74 LONG TERM...Thursday through Monday night...The long term will be characterized by a bit of unsettled weather followed by drier conditions through the weekend ahead of another system. Mountain snow will start the long term followed by rain. Temperatures will begin on the cooler side before returning to near normal over the weekend. Models are in slight agreement with the trough over the area before departing by Thursday night. The most active day of the long term so far will be Thursday with the chances of mountain snow being the highest. With that said, the NBM probabilities of snow over the Wa Cascades is 89%, Or Cascades is 99% and the Blue mountains is 50% for 1 inch of snow Thursday. Snow levels on Thursday will begin around 1200ft before rising to near 4000ft. EFI does show that much of the region will still be under the seasonal average with temperatures in the low 60s across the Basin, 50s in the Gorge, Kittitas/Yakima Valleys, Central Or and the foothills of the Blues and in the 40s elsewhere. Friday through Saturday night the models are in slight agreement with the incoming ridge. All models show the ridge coming in Friday and remaining through Saturday night with variances in the amplitude and timing. GFS has the ridge breaking down and becoming more zonal as the next trough moves in from the BC coast, ECMWF and Canadian models show the ridge remaining but more to the east. All show some precipitation beginning to move in ahead of the trough. EFI shows that Friday through Sunday will begin to hedge towards normal temperatures each day with highs in the mid 60s in the Basin, Yakima Valley, Gorge and along the foothills of the Blues, 50s in Central Or and Kittitas Valley and elsewhere in the 40s. Temperatures will steadily increase each day with Sunday being the warmest day of the period with temperatures nudging the high 60s and 70s in the Gorge, foothills of the Blues, Basin and adjacent Valleys, Central Or and the adjacent Valleys with high 40s to low 50s elsewhere. The models begin to truly diverge by Sunday into Monday with very little agreement. All models are showing different outcomes and clusters are all over the place. For now have just continued with the NBM guidance for the end of the forecast period which has precipitation returning to the forecast area Sunday morning across the mountains before sweeping across the region through Monday. Bennese/90 AVIATION...00Z TAFs...VFR conditions currently observed at all sites, which will stay the course through the period. Showers are expected for PDT/ALW through the evening before drier conditions ensue by 07Z. Winds will stay breezy with gusts of 20-30kts out of the southwest for all sites, with the exception of DLS which winds will stay below 10kts through Tuesday afternoon. Wind gust observations are already above 20kts for RDM/BDN/PDT, with ALW/PSC joining after 06Z and YKM early Tuesday morning. 75 && .PRELIMINARY POINT TEMPS/POPS... PDT 34 51 33 51 / 70 10 10 30 ALW 37 54 36 54 / 80 10 10 50 PSC 39 57 38 58 / 50 0 0 10 YKM 29 53 30 54 / 30 10 0 10 HRI 35 56 35 57 / 50 10 0 10 ELN 29 49 30 50 / 40 10 0 10 RDM 26 45 28 44 / 20 10 10 20 LGD 30 43 28 44 / 80 30 10 70 GCD 27 43 28 44 / 80 20 10 60 DLS 34 55 36 54 / 20 20 20 20 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory until 5 AM PDT Tuesday for ORZ509. WA...Freeze Warning from 2 AM to 9 AM PDT Tuesday for WAZ026-027. Freeze Warning from 2 AM to 9 AM PDT Wednesday for WAZ026-027. && $$ SHORT TERM...75 LONG TERM....90 AVIATION...75